CNS (Central Nervous System) consisting of brain and spinal cord which plays a main role in regulating life phenomenon is a essential organ governing all the human function through from sensory and (in)voluntary movement to thinking, memory, motion, language etc. Accordingly, a rapidly progressed apoptosis of neuronal cell caused by stroke, trauma etc as well as slowly progressed apoptosis such as degenerative disease occurring in CNS caused by senile dementia for example, Alzheimer's disease or Parkinson disease etc result in irreversible functional disorder of neuronal network, which give rise to immortal failure of human function in the end. Among them, the patients suffering from Alzheimer disease, a representative senile dementia have been increased in proportion to both of extended life-span and modernized welfare facility. According to the public survey of Korea Institute for Health and Social Affair, the ratio of older people among Korean people exceeds 7% in 2000, reaches to 8.3% (3,970,000) and shall approach to 14.4% in 2019. Especially, the ratio of more than 65 years old patient suffering with senile dementia is presumed to 8.2% in Korea. In Western countries, about 10% among more than 65 years old and about 40-50% among 80 years old patient suffers with senile dementia. Since more than five million patients suffer with the disease, the medical expense caused thereby is presumed to hundred billion dollars in a year. There have been found that more than about two hundred thousand people are suffering from dementia in Korea. In America, it has been presumed the number of the patients be increased to two fold than the number of present patients in 2030 and fourteen million (more than 350%) in 2050.
Since Alzheimer's disease initiated with cognitive function disorder is one of long-term degenerative diseases resulting in the breakdown of human nature, there have been tried to develop effective and preventive drugs till now, for example, acetylcholineesterase inhibitor such as Aricept® (Pfizer Co.), Exelon (Novartis Co.), Reiminyl® (Janssen Co.) or NMDA receptor antagonist such as Ebixa (Lundbeck Co.). However, the acetylcholine esterase inhibitor could just alleviate reduced cognitive ability and could not satisfactorily treat etiological cause of the disease. Although the drug shows temporarily alleviated effect on only some of patients (about 40-50%), it could not maintain it's potency for a long time moreover it shows various adverse response such as hepato-toxicity, vomiting, anorexia in case of long-term treatment. Accordingly, there has been urgently needed to develop new therapeutic agent to prevent and treat the disease nowadays. Many multi-national pharmaceutical companies have been invested on the development in a large scale and in particular, focused in the development for beta- or gamma secretase inhibitor reducing the reproduced amount of beta-amyloid consisting of about 40 amino acids which has been presumed to be an etiological factor of Alzheimer disease. The basic study on the Alzheimer disease has been actively attempted in Korea however the development of Alzheimer treating agent has been merely progressed till now. Since there have been found in animal model test as well as clinical trial that the development of gamma secretase inhibitor is associated with considerable toxicity, it has been proved to be not recommendable whereas the development of beta secretase inhibitor is recommendable as proven by gene deficiency transformed animal model test. It is also regarded as a safe tool to focus on targeting the factors involved in beta amyloid aggregation. There has been reported that ‘phenserine’ developed by Axonyx Co. in USA has been progressed in Clinical trial 2 phase and it shows dual activities of inhibiting cholinesterase as well as beta amyloid aggregation. (Greig et al., J. Med. Chem., 44, pp. 4062-4071, 2001; www.medicalnewstoday.com; www.alzforum.org/drg/drc)
The development of vaccine using beta amyloid has been known as another possible method. There has been reported that the serial study on the vaccine progressed by Elan Co. failed because of its un-predictable adverse response such as encephalitis during clinical trial. However, it has been reported that beta amyloid vaccine could alleviate cognitive function in animal model test and improve the activity of brain cell as well as damaged brain neuronal cells, resulting in alleviating Alzheimer syndrome. (Janus et al., Nature, 408, pp. 979-982, 2000; Morgan et al., Nature, 408, pp. 982-985, 2000)
To investigate novel benzofuran derivatives having potent inhibiting effect on cognitive function disorder through already well-known screening tests, the inventors of the present invention have intensively screened various benzofuran derivatives showing potent inhibiting activity of beta-amyloid aggregation and memory learning recovery study using passive avoidance test etc, and finally completed present invention by confirming that the benzofuran derivatives inhibits beta-amyloid aggregation and cell cytotoxicity resulting in stimulating the proliferation of neuronal cells as well as recovers memory learning injury caused by neuronal cell injury.
These and other objects of the present invention will become apparent from the detailed disclosure of the present invention provided hereinafter.